At 12:24 PM 11/3/2005, Bob Nielsen wrote:
>On Nov 3, 2005, at 12:02 PM, Jim Lux wrote:
>
> >
> >
> > A rotary joint shouldn't be a big deal for HF. We use a variety of N
> > connector rotary joints on the antenna range at JPL, and they are
> > fairly
> > wide band. I would imagine you could find one surplus.
> >
>
>I used rotary joints for many years when I was working on antenna
>ranges, but don't recall ever seeing any coaxial models with which I
>would feel comfortable running amateur legal limit power levels.
The one I have here, a 2 channel unit, is apparently rated at more than a
kW. I don't know what the limiting component is (is it HV breakdown or
thermal dissipation).
I suspect that they aren't cheap if purchased brand new.
OTOH, if you wanted to make one, for HF, I suspect that you could get "good
enough" if you had access to a competent machinist. It's going to be
hundreds of dollars, regardless.
It might be interesting to scrounge up one of the rotating sign slipring
units and test it RF. They can certainly handle the power. Sort of like
repurposing AC power relays for antenna switch boxes. Not everyone needs a
Transco or Dowkey switch good to 18 GHz at 1.01:1 VSWR.
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